<s>
The	O
OpenBSD	B-Operating_System
operating	B-General_Concept
system	I-General_Concept
focuses	O
on	O
security	O
and	O
the	O
development	O
of	O
security	O
features	O
.	O
</s>
<s>
According	O
to	O
author	O
Michael	O
W	O
.	O
Lucas	O
,	O
OpenBSD	B-Operating_System
"	O
is	O
widely	O
regarded	O
as	O
the	O
most	O
secure	O
operating	B-General_Concept
system	I-General_Concept
available	O
anywhere	O
,	O
under	O
any	O
licensing	O
terms.	O
"	O
</s>
<s>
A	O
common	O
source	O
of	O
error	O
is	O
the	O
misuse	O
of	O
the	O
strcpy	O
and	O
strcat	O
string	O
functions	O
in	O
the	O
C	B-Language
programming	I-Language
language	I-Language
.	O
</s>
<s>
There	O
are	O
two	O
common	O
alternatives	O
,	O
strncpy	O
and	O
strncat	O
,	O
but	O
they	O
can	O
be	O
difficult	O
to	O
understand	O
and	O
easy	O
to	O
misuse	O
,	O
so	O
OpenBSD	B-Operating_System
developers	O
Todd	O
C	B-Language
.	O
Miller	O
and	O
Theo	O
de	O
Raadt	O
designed	O
the	O
strlcpy	O
and	O
strlcat	O
functions	O
.	O
</s>
<s>
They	O
have	O
been	O
adopted	O
by	O
the	O
NetBSD	O
and	O
FreeBSD	O
projects	O
but	O
not	O
by	O
the	O
GNU	B-Language
C	I-Language
Library	I-Language
.	I-Language
</s>
<s>
On	O
OpenBSD	B-Operating_System
,	O
the	O
linker	B-Application
has	O
been	O
changed	O
to	O
issue	O
a	O
warning	O
when	O
unsafe	O
string	O
manipulation	O
functions	O
,	O
such	O
as	O
strcpy	O
,	O
strcat	O
,	O
or	O
sprintf	O
,	O
are	O
found	O
.	O
</s>
<s>
All	O
occurrences	O
of	O
these	O
functions	O
in	O
the	O
OpenBSD	B-Operating_System
source	O
tree	O
have	O
been	O
replaced	O
.	O
</s>
<s>
In	O
addition	O
,	O
a	O
static	O
bounds	O
checker	O
is	O
included	O
in	O
OpenBSD	B-Operating_System
in	O
an	O
attempt	O
to	O
find	O
other	O
common	O
programming	O
mistakes	O
at	O
compile	O
time	O
.	O
</s>
<s>
Other	O
security-related	O
APIs	B-Application
developed	O
by	O
the	O
OpenBSD	B-Operating_System
project	I-Operating_System
include	O
issetugid	O
and	O
arc4random	O
.	O
</s>
<s>
The	O
project	O
in	O
progress	O
modifies	O
the	O
linker	B-Application
so	O
that	O
on	O
every	O
boot	O
,	O
the	O
kernel	O
is	O
relinked	O
,	O
as	O
well	O
as	O
all	O
other	O
randomizations	O
.	O
</s>
<s>
OpenBSD	B-Operating_System
integrates	O
several	O
technologies	O
to	O
help	O
protect	O
the	O
operating	B-General_Concept
system	I-General_Concept
from	O
attacks	O
such	O
as	O
buffer	B-General_Concept
overflows	I-General_Concept
or	O
integer	B-Error_Name
overflows	I-Error_Name
.	O
</s>
<s>
Developed	O
by	O
Hiroaki	O
Etoh	O
,	O
ProPolice	O
is	O
a	O
GCC	B-Application
extension	O
designed	O
to	O
protect	O
applications	O
from	O
stack-smashing	B-General_Concept
attacks	I-General_Concept
.	O
</s>
<s>
It	O
does	O
this	O
through	O
a	O
number	O
of	O
operations	O
:	O
local	O
stack	O
variables	O
are	O
reordered	O
to	O
place	O
buffers	O
after	O
pointers	O
,	O
protecting	O
them	O
from	O
corruption	O
in	O
case	O
of	O
a	O
buffer	B-General_Concept
overflow	I-General_Concept
;	O
pointers	O
from	O
function	O
arguments	O
are	O
also	O
placed	O
before	O
local	O
buffers	O
;	O
and	O
a	O
canary	O
value	O
is	O
placed	O
after	O
local	O
buffers	O
which	O
,	O
when	O
the	O
function	O
exits	O
,	O
can	O
sometimes	O
be	O
used	O
to	O
detect	O
buffer	B-General_Concept
overflows	I-General_Concept
.	O
</s>
<s>
It	O
was	O
integrated	O
in	O
OpenBSD	B-Operating_System
's	O
version	O
GCC	B-Application
in	O
December	O
2002	O
,	O
and	O
first	O
made	O
available	O
in	O
OpenBSD	B-Operating_System
3.3	O
;	O
it	O
was	O
applied	O
to	O
the	O
kernel	O
in	O
release	O
3.4	O
.	O
</s>
<s>
The	O
extension	O
works	O
on	O
all	O
the	O
CPU	O
architectures	O
supported	O
by	O
OpenBSD	B-Operating_System
and	O
is	O
enabled	O
by	O
default	O
,	O
so	O
any	O
C	B-Language
code	O
compiled	O
will	O
be	O
protected	O
without	O
user	O
intervention	O
.	O
</s>
<s>
In	O
May	O
2004	O
,	O
OpenBSD	B-Operating_System
on	O
the	O
SPARC	B-Architecture
platform	O
received	O
further	O
stack	O
protection	O
in	O
the	O
form	O
of	O
StackGhost	O
.	O
</s>
<s>
This	O
makes	O
use	O
of	O
features	O
of	O
the	O
SPARC	B-Architecture
architecture	O
to	O
help	O
prevent	O
exploitation	O
of	O
buffer	B-General_Concept
overflows	I-General_Concept
.	O
</s>
<s>
OpenBSD	B-Operating_System
3.4	O
introduced	O
W^X	O
,	O
a	O
memory	O
management	O
scheme	O
to	O
ensure	O
that	O
memory	O
is	O
either	O
writable	O
or	O
executable	O
,	O
but	O
never	O
both	O
,	O
which	O
provides	O
another	O
layer	O
of	O
protection	O
against	O
buffer	B-General_Concept
overflows	I-General_Concept
.	O
</s>
<s>
While	O
this	O
is	O
relatively	O
easy	O
to	O
implement	O
on	O
a	O
platform	O
like	O
x86-64	B-Device
,	O
which	O
has	O
hardware	O
support	O
for	O
the	O
NX	B-General_Concept
bit	I-General_Concept
,	O
OpenBSD	B-Operating_System
is	O
one	O
of	O
the	O
few	O
OSes	O
to	O
support	O
this	O
on	O
the	O
generic	O
i386	O
platform	O
,	O
which	O
lacks	O
built	O
in	O
per-page	O
execute	O
controls	O
.	O
</s>
<s>
During	O
the	O
development	O
cycle	O
of	O
the	O
3.8	O
release	O
,	O
changes	O
were	O
made	O
to	O
the	O
malloc	B-Language
memory	O
management	O
functions	O
.	O
</s>
<s>
In	O
traditional	O
Unix	O
operating	B-General_Concept
systems	I-General_Concept
,	O
malloc	B-Language
allocates	O
more	O
memory	O
by	O
extending	O
the	O
Unix	O
data	O
segment	O
,	O
a	O
practice	O
that	O
has	O
made	O
it	O
difficult	O
to	O
implement	O
strong	O
protection	O
against	O
security	O
problems	O
.	O
</s>
<s>
The	O
malloc	B-Language
implementation	O
now	O
in	O
OpenBSD	B-Operating_System
makes	O
use	O
of	O
the	O
mmap	B-Operating_System
system	B-Operating_System
call	I-Operating_System
,	O
which	O
was	O
modified	O
so	O
that	O
it	O
returns	O
random	O
memory	O
addresses	O
and	O
ensures	O
that	O
different	O
areas	O
are	O
not	O
mapped	O
next	O
to	O
each	O
other	O
.	O
</s>
<s>
These	O
features	O
make	O
program	O
bugs	O
easier	O
to	O
detect	O
and	O
harder	O
to	O
exploit	O
:	O
instead	O
of	O
memory	O
being	O
corrupted	O
or	O
an	O
invalid	O
access	O
being	O
ignored	O
,	O
they	O
often	O
result	O
in	O
a	O
segmentation	B-Error_Name
fault	I-Error_Name
and	O
abortion	O
of	O
the	O
process	O
.	O
</s>
<s>
This	O
has	O
brought	O
to	O
light	O
several	O
issues	O
with	O
software	O
running	O
on	O
OpenBSD	B-Operating_System
3.8	O
,	O
particularly	O
with	O
programs	O
reading	O
beyond	O
the	O
start	O
or	O
end	O
of	O
a	O
buffer	O
,	O
a	O
type	O
of	O
bug	O
that	O
would	O
previously	O
not	O
be	O
detected	O
directly	O
but	O
can	O
now	O
cause	O
an	O
error	O
.	O
</s>
<s>
One	O
of	O
the	O
goals	O
of	O
the	O
OpenBSD	B-Operating_System
project	I-Operating_System
is	O
the	O
integration	O
of	O
facilities	O
and	O
software	O
for	O
strong	O
cryptography	O
into	O
the	O
core	O
operating	B-General_Concept
system	I-General_Concept
.	O
</s>
<s>
To	O
this	O
end	O
,	O
a	O
number	O
of	O
low-level	O
features	O
are	O
provided	O
,	O
including	O
a	O
source	O
of	O
strong	O
pseudo	B-Algorithm
random	I-Algorithm
numbers	I-Algorithm
;	O
built-in	O
cryptographic	B-Algorithm
hash	I-Algorithm
functions	I-Algorithm
and	O
transforms	O
;	O
and	O
support	O
for	O
cryptographic	O
hardware	O
(	O
OpenBSD	B-Operating_System
Cryptographic	O
Framework	O
)	O
.	O
</s>
<s>
These	O
abilities	O
are	O
used	O
throughout	O
OpenBSD	B-Operating_System
,	O
including	O
the	O
bcrypt	B-Algorithm
password-hashing	O
algorithm	O
derived	O
from	O
Bruce	O
Schneier	O
's	O
Blowfish	B-Algorithm
block	O
cipher	O
,	O
which	O
takes	O
advantage	O
of	O
the	O
CPU-intensive	O
Blowfish	B-Algorithm
key	I-Algorithm
schedule	O
,	O
making	O
brute-force	O
attacks	O
less	O
practical	O
.	O
</s>
<s>
To	O
protect	O
sensitive	O
information	O
such	O
as	O
passwords	O
from	O
leaking	O
on	O
to	O
disk	O
,	O
where	O
they	O
can	O
persist	O
for	O
many	O
years	O
,	O
OpenBSD	B-Operating_System
supports	O
encryption	O
of	O
the	O
swap	O
partition	O
.	O
</s>
<s>
The	O
swap	O
space	O
is	O
split	O
up	O
into	O
many	O
small	O
regions	O
that	O
are	O
each	O
assigned	O
their	O
own	O
encryption	O
key	O
:	O
as	O
soon	O
as	O
the	O
data	O
in	O
a	O
region	O
is	O
no	O
longer	O
required	O
,	O
OpenBSD	B-Operating_System
securely	O
deletes	O
it	O
by	O
discarding	O
the	O
encryption	O
key	O
.	O
</s>
<s>
This	O
feature	O
is	O
enabled	O
by	O
default	O
in	O
OpenBSD	B-Operating_System
3.8	O
and	O
later	O
.	O
</s>
<s>
The	O
network	B-Protocol
stack	I-Protocol
also	O
makes	O
heavy	O
use	O
of	O
randomization	O
to	O
increase	O
security	O
and	O
reduce	O
the	O
predictability	O
of	O
various	O
values	O
that	O
may	O
be	O
of	O
use	O
to	O
an	O
attacker	O
,	O
including	O
TCP	B-Protocol
initial	O
sequence	B-Protocol
numbers	I-Protocol
and	O
timestamps	O
,	O
and	O
ephemeral	O
source	O
ports	O
.	O
</s>
<s>
A	O
number	O
of	O
features	O
to	O
increase	O
network	O
resilience	O
and	O
availability	O
,	O
including	O
countermeasures	O
for	O
problems	O
with	O
ICMP	B-Protocol
and	O
software	O
for	O
redundancy	O
,	O
such	O
as	O
CARP	B-Application
and	O
pfsync	B-Protocol
,	O
are	O
also	O
included	O
.	O
</s>
<s>
The	O
project	O
was	O
the	O
first	O
to	O
disable	O
the	O
plain-text	O
telnet	B-Protocol
daemon	O
in	O
favor	O
of	O
the	O
encrypted	O
SSH	B-Protocol
daemon	O
,	O
in	O
1999	O
,	O
and	O
features	O
other	O
integrated	O
cryptographic	O
software	O
such	O
as	O
IPsec	B-Protocol
.	O
</s>
<s>
The	O
telnet	B-Protocol
daemon	O
was	O
completely	O
removed	O
from	O
OpenBSD	B-Operating_System
in	O
2005	O
before	O
the	O
release	O
of	O
OpenBSD	B-Operating_System
version	O
3.8	O
.	O
</s>
<s>
The	O
OpenBSD	B-Operating_System
project	I-Operating_System
had	O
invented	O
their	O
own	O
utility	O
for	O
cryptographic	O
signing	O
and	O
verification	O
of	O
files	O
,	O
signify	O
,	O
instead	O
of	O
using	O
existing	O
standards	O
and	O
software	O
such	O
as	O
OpenPGP	O
and	O
GnuPG	B-Application
.	O
</s>
<s>
The	O
creator	O
of	O
the	O
signify	O
utility	O
,	O
Ted	O
Unangst	O
,	O
wrote	O
in	O
2015	O
,	O
speaking	O
of	O
OpenPGP	O
and	O
GnuPG	B-Application
:	O
"	O
The	O
concerns	O
I	O
had	O
using	O
an	O
existing	O
tool	O
were	O
complexity	O
,	O
quality	O
,	O
and	O
complexity.	O
"	O
</s>
<s>
signify	O
is	O
integrated	O
into	O
the	O
base	O
operating	B-General_Concept
system	I-General_Concept
and	O
used	O
for	O
verification	O
of	O
all	O
releases	O
,	O
patches	O
,	O
and	O
packages	O
starting	O
with	O
OpenBSD	B-Operating_System
5.5	O
.	O
</s>
<s>
In	O
contrast	O
,	O
other	O
Free	B-Application
Software	I-Application
operating	B-General_Concept
systems	I-General_Concept
and	O
security-focused	O
software	O
tend	O
to	O
use	O
OpenPGP	O
for	O
release	O
verification	O
,	O
and	O
as	O
of	O
2022	O
continue	O
to	O
do	O
so	O
,	O
including	O
:	O
Debian	O
,	O
a	O
prominent	O
operating	B-General_Concept
system	I-General_Concept
that	O
's	O
also	O
used	O
as	O
a	O
base	O
for	O
other	O
operating	B-General_Concept
systems	I-General_Concept
,	O
including	O
Ubuntu	B-Operating_System
;	O
Kali	O
Linux	O
,	O
a	O
specialized	O
operating	B-General_Concept
system	I-General_Concept
for	O
penetration	O
testing	O
,	O
security	O
research	O
,	O
digital	O
forensics	O
,	O
and	O
reverse	O
engineering	O
;	O
Qubes	O
OS	O
,	O
a	O
security-focused	O
operating	B-General_Concept
system	I-General_Concept
;	O
Tor	B-Operating_System
Browser	I-Operating_System
,	O
an	O
anonymous	O
Web	B-Application
browser	I-Application
;	O
SecureDrop	B-Application
,	O
a	O
software	O
package	O
for	O
journalists	O
and	O
whistleblowers	O
to	O
exchange	O
information	O
securely	O
and	O
anonymously	O
over	O
the	O
Internet	O
;	O
and	O
VeraCrypt	B-Operating_System
,	O
a	O
software	O
program	O
for	O
on-the-fly	O
encryption	O
and	O
full	O
disk	O
encryption	O
.	O
</s>
<s>
In	O
X11	B-Operating_System
on	O
OpenBSD	B-Operating_System
,	O
neither	O
the	O
X	B-Operating_System
server	B-Operating_System
nor	O
X	B-Operating_System
clients	O
normally	O
have	O
any	O
escalated	O
direct	O
memory	O
or	O
hardware	O
privileges	O
:	O
When	O
driving	O
X	B-Operating_System
with	O
the	O
Intel(4 )	O
or	O
Radeon(4 )	O
drivers	O
,	O
these	O
normally	O
interact	O
with	O
the	O
underlying	O
hardware	O
via	O
the	O
Direct	O
Rendering	O
Management(4 )	O
kernel	O
interface	O
only	O
,	O
so	O
that	O
lowlevel	O
memory/hardware	O
access	O
is	O
handled	O
solely	O
by	O
the	O
kernel	O
.	O
</s>
<s>
For	O
this	O
reason	O
,	O
X11	B-Operating_System
on	O
OpenBSD	B-Operating_System
does	O
not	O
open	O
up	O
lowlevel	O
memory	O
or	O
hardware	O
access	O
to	O
user/root	O
programs	O
as	O
is	O
done	O
on	O
some	O
other	O
systems	O
,	O
and	O
as	O
was	O
done	O
in	O
the	O
past	O
,	O
which	O
then	O
needed	O
the	O
user	O
to	O
escalate	O
the	O
machdep.allowaperture	O
setting	O
from	O
its	O
default	O
zero	O
setting	O
,	O
to	O
an	O
unsecure	O
setting	O
.	O
</s>
<s>
OpenBSD	B-Operating_System
's	O
version	O
of	O
the	O
X	B-Operating_System
Window	I-Operating_System
System	I-Operating_System
(	O
named	O
Xenocara	B-Application
)	O
has	O
some	O
security	O
modifications	O
.	O
</s>
<s>
The	O
server	B-Operating_System
and	O
some	O
of	O
the	O
default	O
applications	O
are	O
patched	O
to	O
make	O
use	O
of	O
privilege	O
separation	O
,	O
and	O
OpenBSD	B-Operating_System
provides	O
an	O
"	O
aperture	O
"	O
driver	O
to	O
limit	O
X	B-Operating_System
's	O
access	O
to	O
memory	O
.	O
</s>
<s>
However	O
,	O
after	O
work	O
on	O
X	B-Operating_System
security	O
flaws	O
by	O
Loïc	O
Duflot	O
,	O
Theo	O
de	O
Raadt	O
commented	O
that	O
the	O
aperture	O
driver	O
was	O
merely	O
"	O
the	O
best	O
we	O
can	O
do	O
"	O
and	O
that	O
X	B-Operating_System
"	O
violates	O
all	O
the	O
security	O
models	O
you	O
will	O
hear	O
of	O
in	O
a	O
university	O
class.	O
"	O
</s>
<s>
He	O
went	O
on	O
to	O
castigate	O
X	B-Operating_System
developers	O
for	O
"	O
taking	O
their	O
time	O
at	O
solving	O
this	O
>	O
10-year-old	O
problem.	O
"	O
</s>
<s>
On	O
November	O
29	O
,	O
2006	O
,	O
a	O
VESA	B-Device
kernel	O
driver	O
was	O
developed	O
that	O
permitted	O
X	B-Operating_System
to	O
run	O
,	O
albeit	O
more	O
slowly	O
,	O
without	O
the	O
use	O
of	O
the	O
aperture	O
driver	O
.	O
</s>
<s>
On	O
February	O
15	O
,	O
2014	O
,	O
X	B-Operating_System
was	O
further	O
modified	O
to	O
allow	O
it	O
to	O
run	O
without	O
root	O
privileges	O
.	O
</s>
<s>
After	O
the	O
discovery	O
of	O
a	O
security	O
vulnerability	O
in	O
X	B-Operating_System
,	O
OpenBSD	B-Operating_System
does	O
n't	O
support	O
the	O
running	O
of	O
X	B-Operating_System
as	O
a	O
root	O
user	O
and	O
only	O
supports	O
running	O
X	B-Operating_System
via	O
a	O
display	O
manager	O
as	O
a	O
dedicated	O
_x11	O
user	O
.	O
</s>
<s>
Many	O
of	O
these	O
have	O
been	O
applied	O
to	O
the	O
OpenBSD	B-Operating_System
versions	O
of	O
common	O
programs	O
such	O
as	O
tcpdump	B-Protocol
and	O
Apache	B-Application
,	O
and	O
to	O
the	O
BSD	B-Operating_System
Authentication	I-Operating_System
system	O
.	O
</s>
<s>
OpenBSD	B-Operating_System
has	O
a	O
history	O
of	O
providing	O
its	O
users	O
with	O
full	O
disclosure	O
in	O
relation	O
to	O
various	O
bugs	O
and	O
security	O
breaches	O
detected	O
by	O
the	O
OpenBSD	B-Operating_System
team	O
.	O
</s>
<s>
In	O
OpenBSD	B-Operating_System
5.3	O
,	O
support	O
for	O
full	O
disk	O
encryption	O
was	O
introduced	O
,	O
but	O
enabling	O
it	O
during	O
the	O
installation	O
of	O
OpenBSD	B-Operating_System
had	O
required	O
manual	O
intervention	O
from	O
the	O
user	O
by	O
exiting	O
the	O
installer	O
and	O
entering	O
some	O
commands	O
.	O
</s>
<s>
Starting	O
from	O
OpenBSD	B-Operating_System
7.3	O
,	O
the	O
installer	O
supports	O
enabling	O
full	O
disk	O
encryption	O
using	O
a	O
guided	O
procedure	O
,	O
not	O
requiring	O
manual	O
intervention	O
anymore	O
.	O
</s>
<s>
OpenBSD	B-Operating_System
5.9	O
included	O
support	O
for	O
the	O
then	O
–	O
new	O
pledge	O
system	B-Operating_System
call	I-Operating_System
(	O
introduced	O
in	O
OpenBSD	B-Operating_System
5.8	O
as	O
tame	O
and	O
renamed	O
in	O
5.9	O
to	O
pledge	O
)	O
for	O
restricting	O
process	O
capabilities	O
to	O
a	O
minimal	O
subset	O
required	O
for	O
correct	O
operation	O
.	O
</s>
<s>
Since	O
its	O
introduction	O
,	O
applications	O
and	O
ports	O
have	O
been	O
changed	O
to	O
support	O
pledge	O
,	O
including	O
the	O
Chromium	B-Language
web	I-Language
browser	I-Language
.	O
</s>
<s>
OpenBSD	B-Operating_System
6.4	O
introduced	O
the	O
unveil	O
system	B-Operating_System
call	I-Operating_System
for	O
restricting	O
filesystem	B-Application
visibility	O
to	O
a	O
minimum	O
level	O
.	O
</s>
